When did our story start? Well, our family split from the other apes 7 – 14 million years ago. But of course, those first members of the human family weren’t recognisably human. Our species – Homo sapiens or “anatomically modern humans” – didn’t evolve for millions of years.
The traditional date for the origin of the first humans is between 150 – 200,000 years ago; based on fossil and genetic evidence. This would make us basically babies from our family’s perspective.
But the thing about genetic and fossil evidence is that there’s always the chance we can find some more. And a series of new discoveries have done just that. New fossils and genetic samples from Africa seem to have added an extra 100 – 200 thousand years onto our species’ history.
Alas, that’s not quite enough to change our status as the youngest sibling of the human family. However, this added (pre)history does shake up our understanding of the first humans quite a bit.
Genes of the first humans
Ok, that subheading is a bit of a lie. We haven’t found the genes of the first humans. We’ve found the genes of ancient people living in Africa 2,000 years ago. Now, on the surface that doesn’t seem that important. After all, we’ve found ancient DNA several orders of magnitudes older. From different species! What could DNA a mere 2,000 years old tell us?
Well, the significance stems from its age and location. Whilst we’ve found a lot of ancient DNA before (or aDNA if you want to be lazy), almost none of it is African. This is significant because Africa is where we evolved, so that’s where the first splits between populations happened. If you want to work backwards and figure out the last common ancestor of all human populations, that’s where you need to look.
Currently, the first such split amongst humans we’ve found was between the Khoe-San and everyone else. By comparing the differences between their genomes we’ve calculated that this happened around 160,000 years ago. Since both groups are fully human, this strongly suggests that the first humans were living at least this long ago.
But this 2,000 year old aDNA is where things get all shook up. It belonged to a hunter-gatherer living in Ballito Bay, South Africa. Based on genetic divergence, this person belonged to a group that split even earlier than the Khoe-San. This Ballito Bay dude’s family diverged from everyone else at least 260,000 years ago.
This just happens to be consistent with . . .
“New” ancient fossils
Until now, the oldest modern human fossils we’d found date back to 195,000 years ago. This does line up neatly with the dates of the first humans given by the Khoe-San genetic data.
But now we’ve got the older split of Ballito Bay. Where are their fossils? Well, 3 days after the genetic results went up a new fossil was found to go along with them. Coincidence? Or maybe the whole thing is too neat and evolution really is a conspiracy.
Well, the latest fossils to be planted by Satan come from Jebel Irhoud, Morocco. The site has been known about since the 60s, but it’s making the news again because people have done some more digging there. This turned up a skull which was shared many key similarities with more recent modern humans.
But what makes this skull interesting is that it isn’t actually that recent, despite its appearance. The skull was dated through multiple methods to ~315 kya; more than 100,000 years older than the next known human skull. Whilst this is consistent with the “more than 260,000 years” origin suggested by Ballito Bay, it’s different enough that we wouldn’t get suspicious of Satan’s involvement.
Is it finally sorted?
With all this extra data, is the origin of the first humans finally figured out? Unlikely. This research comes with a fair few caveats that suggest the human family tree still needs a bit more sorting out.
Notably, the Jebel skull still raises some questions that need answering. Like the other early fossils of humans, it does differ from modern humans in a few ways. In this case, whilst their face is fairly modern the rest of their skull is still fairly long and flat. This is unlike our tall, rounded head a bit more similar to other hominin species like the Neanderthals.
And so, like with these other fossils, there’s debate over where they fit into our evolution. Are they simply an early variant of our species? Or are these differences significant enough that they shouldn’t be considered Homo sapiens? The differences in the skull could prove important. Perhaps it means their brain was fairly different to our own, indicating it should be considered distinct.
Unfortunately, we’re unlikely to get an answer anytime soon. There just aren’t enough fossils from this period to answer these questions. Yet. More bones could obviously help clear this up. When we find them is a different question.
Even the genetics isn’t completely certain. The research into Ballito Bay genetics found that most later populations interbred with other, more recent African populations. Even the ancient Khoe-San had more hanky panky that was previously thought. The resulting influx of “new” genes could cause their genetic age to be underestimated. Perhaps if we could find some “undiluted” aDNA from them they might also claim a more ancient origin.
So, about those first humans
What does all of this mean for when the first humans evolved? Well, genetic data indicates our last common ancestor was at least 260,000 years ago. I think it’s pretty obvious they’d be modern humans. We also have some fossils from around this time. We can’t say for sure whether they’d be in our immediate family tree. Whether or not they’re even a candidate depends on how significant you think the differences between us are. And that’s something we can’t really answer with the fossils we have.
Which is all great for me because I get to squeeze more blog posts out of all this speculation!
Hublin, J.J., Ben-Ncer, A., Bailey, S.E., Freidline, S.E., Neubauer, S., Skinner, M.M., Bergmann, I., Le Cabec, A., Benazzi, S., Harvati, K. and Gunz, P., 2017. New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens. Nature, 546(7657), pp.289-292.
Schlebusch, C.M., Malmström, H., Günther, T., Sjödin, P., Coutinho, A., Edlund, H., Munters, A.R., Steyn, M., Soodyall, H., Lombard, M. and Jakobsson, M., 2017. Ancient genomes from southern Africa pushes modern human divergence beyond 260,000 years ago. bioRxiv, p.145409.